/ Dictionary / Index I isoniazid: Meaning and Definition of Find definitions for: i•so•ni•a•zid Pronunciation: (ī"su-nī'u-zid), [key] — n. Pharm. a white, crystalline, water-soluble solid, CHNO, used in the treatment of tuberculosis. Random House Unabridged Dictionary, Copyright © 1997, by Random House, Inc., on Infoplease. See also: isoniazid (Thesaurus) isoneph isonicotinic acid hydrazide Related Content Daily Word Quiz: sequester Analogy of the Day: Today’s Analogy Spelling Bee: Today’s Spelling Bee Frequently Misspelled Words Frequently Mispronounced Words Easily Confused Words Writing & Language